I took an .rtf ( which used Times New Roman - family) imported into Calibre, converted to a .mobi opened on the Kindle Previewer for Mac. I see that the book looks OK except for the font and some places where the text was italicized in certain areas are not italicized now viewing in the KP. I then looked at the mobi in my Kindle Fire and I see the same thing ( now the KF you can change the fonts and I tried that but the italicized areas that were in the original .rtf are different.

So I experimented by changing the font family in the rtf to (arial) then impoted to Calibre saved as another .mobi

This time the file moved some styles around incorrectly causing mis aligned paragraphs all over the document.

Then I tried to open the rtf within word, save as a webpage ( filtered) opened that saved doc in Calibre, imported to .mobi and when I looked at that in the KPreviewer I see the same font style as the rtf version but now the paragraph structure in alot of spots thru out the book are justified where they should not be , mis aligned badly,

So I went back to the original Times new Roman rtf exported as a mobi which gave me the best result. is there another way of doing this that I should know about?